TYPING MACHINE KEY ACTION

摘要

A key lever is pivotally connected to a horizontal arm of a bell crank in a typing machine key action, and a coil tension spring is connected between a vertical arm of the bell crank and a vertical arm of a horizontal interposer. Depression of the key lever pivots the bell crank to stretch the coil tension spring. When the descending key lever pushes the horizontal interposer off a ledge, the coil tension spring snaps the horizontal interposer to the rear against a pawl that engages a power roll to initiate a typing operation. A bendable tab that limits downward movement of the key lever can be bent out of the way so that the key lever can be depressed further into a repeat position thus enabling the same parts to be used for both single-action and repeat key actions. In another embodiment of the invention, a longitudinal slot is formed in the horizontal arm of the bell crank to compensate for key levers having different lengths. In both embodiments of the invention, the bell crank permits the use of a horizontal interposer thus enabling the typing machine to have an aesthetically pleasing low silhouette.